1. Field of the Invention
The present invention relates generally to a process for the sulfiding of a hydrodesulfurization catalyst in a distillation column reactor. More particularly the invention relates to a process wherein a sulfiding agent such as H2S and a solvent are concurrently fed through a distillation column containing a hydrodesulfurization catalyst that contain hydrogenation metals in their oxide state.
2. Related Information
Hydrodesulfurization is a process for removing organic sulfur compounds from petroleum streams by converting the sulfur in the organic sulfur compounds to H2S. The process necessarily incorporates hydrogenation and thus requires hydrogenation catalysts. Water is also a product of the sulfiding reaction and must be removed.
Catalysts which are useful for the hydrodesulfurization reaction include Group VIII metals such as cobalt, nickel, palladium, alone or in combination with other metals such as molybdenum or tungsten on a suitable support which may be alumina, silica-alumina, titania-zirconia or the like. Normally the metals are provided as the oxides of the metals supported on extrudates or spheres and as such are not generally useful as distillation structures.
The catalyst may also contain components from Group V, and VIB metals of the Periodic Table or mixtures thereof. The Group VIII metal provides increased overall average activity. Catalysts containing a Group VIB metal such as molybdenum and a Group VIII such as cobalt or nickel are preferred. Catalysts suitable for the hydrodesulfurization reaction include cobalt-molybdenum, nickel-molybdenum and nickel-tungsten. The metals are generally present as oxides supported on a base such as alumina, silica-alumina or the like. If the active form of the metal, the sulfide, is exposed to air, it begins to oxidize which can create a hazard.
The catalyst beds as used in the present invention may be described as fixed, meaning positioned in a fixed area of the column and include expanded beds and ebulating beds of catalyst. The catalysts in the beds may all be the same or different so long as they carry out the function of hydrogenation as described. Catalysts prepared as distillation structures are particularly useful in the present invention.
The metals contained in the hydrogenation catalysts must be converted from the stable oxide form to the reduced sulfide form to be useful for hydrodesulfurization. Because of the unique combination reactor distillation column, a unique method of reducing the oxide to the sulfide is needed. Briefly the invention is a process for sulfiding a hydrodesulfurization catalyst which comprises:
(a) drying the catalyst with nitrogen;
(b) supplying the distillation column reactor with a sulfiding solvent, preferably containing organic sulfur;
(c) establishing hydrocarbon feed and hydrogen flow rates;
(d) optionally, recycling of sulfiding solvent to supply tank;
(e) heating the distillation column reactor to a temperature above the decomposition temperature of the sulfiding agent, preferably in the range of 300-500xc2x0 F.;
(f) introducing a sulfiding agent;
(g) observing breakthrough of the sulfiding agent in the overhead and increasing the temperature to a target temperature, preferably in the range of 500-700xc2x0 F., upon said breakthrough; and
(h) holding the target temperature for a period of time.
After the treatment the unit may be switched to normal feed for hydrodesulfurization. The concurrent flow of the sulfiding agent and solvent is preferably upflow but could also be downflow. Hydrogen may also be fed either concurrently or countercurrently. Water by-product is removed overhead when operated in a distillation mode.
The process is preferably operated in a reactive distillation mode, although it can be operated without boiling or distillation. The term xe2x80x9creactive distillationxe2x80x9d is used to describe the concurrent reaction and fractionation in a column. For the purposes of the present invention, the term xe2x80x9ccatalytic distillationxe2x80x9d includes reactive distillation and any other process of concurrent reaction and fractional distillation in a column regardless of the designation applied thereto.